In the related art, as a bearing used for a high-speed rotating body, a thrust bearing is known which is disposed so as to face a thrust collar provided on a rotary shaft. As such a thrust bearing, a foil-type thrust bearing is well known. The foil-type thrust bearing is configured so that wave sheets formed of thin sheets called bump foils are annularly arranged on an annular plate-shaped plate member (base plate) which is a base, and thin sheets called top foils, whose number is the same as the number of the bump foils, are disposed on the bump foils (refer to Patent Documents 1 and 2).
When the foil-type thrust bearing having the above configuration rotates in a state where the thrust collar is close to the thrust bearing surface (top foil), an air film (fluid lubrication film) is formed between the thrust collar and the top foil through the wedge effect, and the foil-type thrust bearing supports the thrust collar through the air film. The wedge effect is a phenomenon in which when a fluid flows from a wide gap into a narrow gap, pressure occurs in the narrow gap. The thrust bearing supports a load (the thrust collar) using this effect, namely using the pressure occurring in the narrow gap.
Therefore, in order to efficiently obtain the wedge effect in the foil-type thrust bearing, it is necessary to change the height of the top foil in the rotational direction of the thrust collar in order that the wide gap and the narrow gap are continuously formed between the thrust collar and the top foil. In order to change the height of the top foil in this way, in the related art, the height of the bump foil (the heights of bumps (peaks)) is changed in the rotational direction of the thrust collar.
In addition, Patent Documents 3 to 6 disclose thrust bearings supporting thrust collars.